1. Field of the Invention
The present invention relates to a method and apparatus for bending a blade member in which a process of bending a strip-like blade member in the width direction, and that of bending the blade member in the thickness direction can be continuously performed.
2. Explanation of Related Art
For example, there is a case where, as shown in principle in FIGS. 36 and 37, notches or perforations are formed in a work W such as paperboard by using a rotary die 100 to which a blade member 1 is attached. In this case, the rotary die 100 is used while being combined with an anvil 200 serving as a receiving roller. In the blade member 1 attached to the rotary die 100, a blade edge 12 which is disposed in one end edge in the width direction is projected from the outer peripheral face of the rotary die 100, and the blade edge 12 is curved into a shape which is parallel to the outer peripheral face of the rotary die 100. The work W is fed as indicated by the arrow between the rotary die 100 and the anvil 200 while rotating the die and the anvil, notches or perforations having a shape corresponding to that of the blade edge 12 of the blade member 1 are formed in the work W. As the anvil 200, either of a member which is made of iron, and in which the surface is hard, and that which is made of rubber or the like, and in which the surface is soft is suitably used.
FIGS. 38 to 40 show an example of a bending procedure for obtaining the blade member 1 attached to the rotary die 100 shown in FIG. 36. FIG. 38 shows a state where the blade member 1 is bent in the thickness direction to be formed into a substantially rectangular shape in a plan view. In this state, the whole blade edge 12 is in a virtual horizontal plane. FIG. 39 shows a state where one side of the rectangular blade member 1 of FIG. 38 is bent in the range from one end portion to an intermediate portion, in the width direction of the blade member 1. As seen from the figure, in this stage, the portion on which the bending work in the width direction is performed is changed into a curved shape in which the shape in a side view of the blade member 1 is swollen, i.e., a curved shape which extends along the outer peripheral face of the rotary die 100. FIG. 40 shows the blade member 1 which is obtained by performing the bending work on one side of the rectangular blade member 1 and the opposed side.
For example, a blade member bending method in which the blade member 1 having a blade edge in one end edge in the width direction is bent in the width direction has been proposed by the assignee of the present invention (see Japanese Patent Application Laying-Open No. 2004-141959). The proposed method includes a compressing/extending step in which a portion in the vicinity of the blade edge is clamped by roller dies from the both sides to compress the portion in the thickness direction, thereby extending the compressed portion in the longitudinal direction. In the compressing/extending step, the dies are rotated and the compressed portion is continuously displaced, whereby the blade member is bent in the width direction.
In the method of bending the blade member 1 in the width direction, however, a blade member which is previously bent in the thickness direction into a desired shape by another thickness-direction bending machine is obtained, and the blade member is bent in the width direction. In this way, the thickness-direction bending process and the width-direction bending process are performed by respective machines in separate places. Therefore, the production efficiency is poor, and the production cost is high.
In the case where a blade member which is previously bent in the thickness direction, there is a problem in that, even when blade members of various curvatures are prepared, a case where a blade member having an adequate curvature matched to the width-direction bending process cannot be found often occurs. In a system of bending a blade member in which the blade member is previously bent in the thickness direction and then bent in the width direction to obtain a complete blade member product, it is difficult to obtain a blade member product in which the bending in the thickness direction accurately coincides with the curvature of the blade member bent in the width direction, or namely it is difficult to obtain a blade member product which has a complex curved shape.